Over the first couple of years, the juveniles ( those that are not
cannibalized, which may account for a partial lack of young specimens in the
fossil record, ) stay relatively close to the adults, foraging scraps from
the adult kills and benefit from the protection of close proximity to the
adults (as long as they aren't eaten themselves!). They also practice their
skills in capturing smaller, benign vertebrates in the underbrush, as an
additional food source and possibly develop a hunting "play" routine, that
will later transform into the associative bond between siblings leading to
"pack" behaviour.

As the juvies continue living in close association, they form a cohesive
bond of sorts and as they rapidly gain in size and explore a larger
territory away from the parental pair (having learned additional hunting
strategies from the parents by watching, enhancing ingrained instinctual
patterns ), they further develop a "pack" sensibility, that allows them to
bring down larger prey through association then they could ever manage
hunting on their own ( a further reinforced behaviour ).

Each succeeding cluster of young derived from the main breeding couple ( if
in fact, adult tyrannosaurs mate for life?), grow up as independent units /
packs, eventually moving off into their own respective territories.

Because their selected prey is generally smaller inhabitants of the
ecosystem than the mature adults are hunting, there is not a significant
overlap in prey competition.

As each pack unit grows into maturity, the inexorable urge to mate ( you
know, raging hormones, etc. . .) start to exert pressures amongst the group,
resulting in aggressive behaviour ( face biting, as recorded in many
tyrannosaurs, etc. . . ). Eventually the pack splits as they seek available
partners outside the family unit to breed with. As subadult to mature adult
animals, they are now more than capable of bringing down sizable prey on
their own, without the assistance of their previous pack members and enter
into a self sufficient lifestyle.

Once a newly formed breeding couple have offspring, they either stay as a
bonded pair ( ala many modern birds ) or separate seeking other compatible
partners later on ( either scenario a paleontological mystery for the time
being ). . . In the peek of their prime, whether as a couple or independent
individuals, these dinosaurs are performing daily functions at peak
capacity.

After the 20 year "milestone", the rigors of life and competition begin to
take an their toll. Injuries, old age and environmental stresses make it
increasingly harder to survive. Scavenging and kleptophagy become MORE
dominant strategies in securing food than hunting live prey did in their
youth ( works both ways, old individuals chase the very young from kills,
while virile 20 year olds drive off old bulls from carcasses ) as both
intraspecific behaviour within species and between other competing predators
( i.e. Gorgosaurs / Daspletosaurs, DP formation, Alberta ). . . prove to be
more and more of a disadvantage to older individuals.

Eventually the oldest die off, either through starvation as inability to
find accessible food sources depletes their energy reserves, or they are
themselves preyed upon by other more ambitious adults (in times when
scarcity of alternate food resource occurs in a particular geographic area,
etc. . .)

Somewhere previously on this thread there was a comment concerning evidence
of "packs" in Tyrannosaurus. I think previously it has been mentioned on
the DML that associated material / in differing growth stages has been found
with Tinker, Sue, etc. . . there a sites with multiple Tarbosaurus remains,
as well as locales preserving similar patterns in most other members of the
the Tyrannosauridae / inae. . . Tom Holtz??

In terms of EQ, intellligence, etc. . . you only have to be smarter than
your intended prey. . . everything is relative. . .